lkml.org 
[lkml]   [2019]   [Dec]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[tip: core/kprobes] x86/alternative: Shrink text_poke_loc
    The following commit has been merged into the core/kprobes branch of tip:

    Commit-ID: 4531ef6a8aaf132aa32e2e26670c652942540633
    Gitweb: https://git.kernel.org/tip/4531ef6a8aaf132aa32e2e26670c652942540633
    Author: Peter Zijlstra <peterz@infradead.org>
    AuthorDate: Wed, 09 Oct 2019 12:26:53 +02:00
    Committer: Ingo Molnar <mingo@kernel.org>
    CommitterDate: Wed, 27 Nov 2019 07:44:24 +01:00

    x86/alternative: Shrink text_poke_loc

    Employ the fact that all text must be within a s32 displacement of one
    another to shrink the text_poke_loc::addr field. Make it relative to
    _stext.

    This then shrinks struct text_poke_loc to 16 bytes, and consequently
    increases TP_VEC_MAX from 170 to 256.

    Tested-by: Alexei Starovoitov <ast@kernel.org>
    Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Acked-by: Alexei Starovoitov <ast@kernel.org>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Josh Poimboeuf <jpoimboe@redhat.com>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Link: https://lkml.kernel.org/r/20191111132458.047052889@infradead.org
    Signed-off-by: Ingo Molnar <mingo@kernel.org>
    ---
    arch/x86/kernel/alternative.c | 23 ++++++++++++++---------
    1 file changed, 14 insertions(+), 9 deletions(-)

    diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
    index 6e3ee73..526cc5f 100644
    --- a/arch/x86/kernel/alternative.c
    +++ b/arch/x86/kernel/alternative.c
    @@ -937,7 +937,7 @@ static void do_sync_core(void *info)
    }

    struct text_poke_loc {
    - void *addr;
    + s32 rel_addr; /* addr := _stext + rel_addr */
    s32 rel32;
    u8 opcode;
    const u8 text[POKE_MAX_OPCODE_SIZE];
    @@ -948,13 +948,18 @@ static struct bp_patching_desc {
    int nr_entries;
    } bp_patching;

    +static inline void *text_poke_addr(struct text_poke_loc *tp)
    +{
    + return _stext + tp->rel_addr;
    +}
    +
    static int notrace patch_cmp(const void *key, const void *elt)
    {
    struct text_poke_loc *tp = (struct text_poke_loc *) elt;

    - if (key < tp->addr)
    + if (key < text_poke_addr(tp))
    return -1;
    - if (key > tp->addr)
    + if (key > text_poke_addr(tp))
    return 1;
    return 0;
    }
    @@ -1000,7 +1005,7 @@ int notrace poke_int3_handler(struct pt_regs *regs)
    return 0;
    } else {
    tp = bp_patching.vec;
    - if (tp->addr != ip)
    + if (text_poke_addr(tp) != ip)
    return 0;
    }

    @@ -1078,7 +1083,7 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries
    * First step: add a int3 trap to the address that will be patched.
    */
    for (i = 0; i < nr_entries; i++)
    - text_poke(tp[i].addr, &int3, sizeof(int3));
    + text_poke(text_poke_addr(&tp[i]), &int3, sizeof(int3));

    on_each_cpu(do_sync_core, NULL, 1);

    @@ -1089,7 +1094,7 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries
    int len = text_opcode_size(tp[i].opcode);

    if (len - sizeof(int3) > 0) {
    - text_poke((char *)tp[i].addr + sizeof(int3),
    + text_poke(text_poke_addr(&tp[i]) + sizeof(int3),
    (const char *)tp[i].text + sizeof(int3),
    len - sizeof(int3));
    do_sync++;
    @@ -1113,7 +1118,7 @@ static void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries
    if (tp[i].text[0] == INT3_INSN_OPCODE)
    continue;

    - text_poke(tp[i].addr, tp[i].text, sizeof(int3));
    + text_poke(text_poke_addr(&tp[i]), tp[i].text, sizeof(int3));
    do_sync++;
    }

    @@ -1143,7 +1148,7 @@ void text_poke_loc_init(struct text_poke_loc *tp, void *addr,
    BUG_ON(!insn_complete(&insn));
    BUG_ON(len != insn.length);

    - tp->addr = addr;
    + tp->rel_addr = addr - (void *)_stext;
    tp->opcode = insn.opcode.bytes[0];

    switch (tp->opcode) {
    @@ -1192,7 +1197,7 @@ static bool tp_order_fail(void *addr)
    return true;

    tp = &tp_vec[tp_vec_nr - 1];
    - if ((unsigned long)tp->addr > (unsigned long)addr)
    + if ((unsigned long)text_poke_addr(tp) > (unsigned long)addr)
    return true;

    return false;
    \
     
     \ /
      Last update: 2019-12-04 09:35    [W:3.878 / U:0.160 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site